United States New York New York County Manhattan Borough
1664 Yorkshire became the first large government unit (not actually a county) organized by New York after the English took control from the Netherlands. It was divided into three ridings including North Riding (Westchester, Bronx, New York (Manhattan), Nassau and part of Queens counties). 
1683 New York ended Yorkshire, creating New York (Manhattan) County from part of it. 
1874 West Bronx was added to New York County.
1895 East Bronx was added to New York County.
1898 The five boroughs were consolidated into New York City and her county governments were dissolved. The Borough of Manhattan became a borough of Greater New York City, with the same borders as the old New York County.
1914 Bronx County, with the same borders as its borough, separated from New York County.